I like going about it the other way around. If you profile and thread the barrel first, you are on the hook to make the chamber perfect the first time. I rough the chamber, then finish it. After close inspection, I cut the blank to about 1/4" longer than the desired barrel length. Then I put the barrel between centers and thread it. After I install the barrel-extension, I proof-test the barrel with one shot. You can inspect the brass carefully for any problems in the chamber, and borescope the throat and bore for any problems as well.
If it passes those "tests" then I profile the barrel, and eventually drill and ream the gas-port. Once you profile it, or drill the gas-port, you are pretty well stuck with what you have. If you end up with a problem in the chamber, and catch it prior to profiling, you can cut the shank off and start over.
With all due respect to MilGunsmith, I have never made any attempt to time the gas-port into a groove. Before I started chambering my own barrels, I took the advise of one of the most respected AR smiths in the country. He doesn't "time" the gas-port to the groove, so I never did either. I drill and ream the port when everything else is done, and have never had any adverse results from where the port ends up. Take care in drilling, reaming and removing any small burr that may remain, and you will be in fine shape.